In the U.S., during past decades, the incidence of non-Hodgkin's lymphoma (NHL) has risen faster than that of all other cancer types except melanoma and lung cancer. Connecticut, one of the states with the greatest increase in NHL incidence, has one of the highest NHL incidence rates in the world. The risk factors responsible for the increasing NHL incidence are largely unknown. A recent prospective follow-up study from American Cancer Society and two recent case-control studies from the NCI found a strong association between dark hair dye use and risk of NHL while another recent follow-up study found no association. It has been suggested that the environmental exposure which seems most likely to have contributed to the increase in NHL among women is that of hair dyes. It is estimated that hair aye use could account for 35% of the NHL occurring in exposed women and 20% in all women. More than 30 million American women are regular hair dye users, and the size of the exposed population is increasing rapidly. Considering the inconclusive nature of the reported association and the size of the exposed population, there exists an urgent need for more rigorous epidemiologic studies in different populations. Against this background and challenge for a clearer understanding of the etiology of NHL, a case-control study of NHL in Connecticut is proposed. The primary objective of the proposed study is to examine hair dye exposure as a NHL risk factor using a population-based case-control study design in Connecticut. More specifically, this study will test the hypotheses that a) use of hair dye is associated with an increased risk of NHL; b) risk of NHL varies by type and color of the hair dye product and c) risk of NHL associated with hair dye use varies by histologic type, immunologic type, and tumor grade. Since very few men (about 5%) regularly use hair dye products, the study will restrict the population to women aged between 21 and 84. Cases will consist of 600 Connecticut female residents with histologically confirmed incident NHL diagnosed over a 3.5 year period. Cases will be identified through an established population-based mechanism of rapid case ascertainment. An equal number of population-based controls will be frequency matched to the cases by aged race, and sex. For cases under age 65, controls will be selected by random digit dialing. For cases aged 65 or older, controls will be randomly selected from files provided by the Health Care Financing Administration. Cases and controls must be alive at the time of interview and will be interviewed at home by trained interviewers using a structured, standardized questionnaire to obtain information regarding hair dye use and other major risk factors. Statistical analyses will be performed using standard techniques to address the questions raised by the specific aims.